Taxonomy, systematics, and life cycles of Azygiids (Digenea: Azygiidae) of the Southeastern United States

Abstract

Digeneans (Platyhelminthes: Trematoda: Digenea) comprise the vast majority of Trematoda, which is one of three entirely parasitic classes within the Platyhelminthes. They are characterized as having complex life cycles involving asexual reproduction in invertebrates, sexual reproduction in vertebrates, and free-living dispersal stages between/among those requisite hosts. In this thesis, using morphology and genetic data, I aimed to taxonomically characterize the life history stages of species of Proterometra Horsfall, 1933 and Leuceruthrus Marshall and Gilbert, 1905 (Digenea: Azygiidae), which undergo asexual reproduction in snails of Pleuroceridae, and mature in the buccal cavity (=Proterometra spp.) and stomach (=Leuceruthrus spp.) of freshwater fishes, primarily those of Centrarchidae. These flukes are unique among other digeneans by having furcocystocercous cercariae that are macroscopic, progenetic (i.e., Proterometra spp.), and when shed from the snail host seemingly mimic a fish prey item thus luring the fish host to consume it. This work has culminated in the taxonomic characterization of life history stages of 5 species of Proterometra and 4 species of Leuceruthrus obtained from 6 river drainages and 4 states, established geographic ranges and summarized all accounts for nominal species of both genera, and provided a taxonomic review/ updated diagnosis for both genera. Additionally, and comprising the largest phylogenetic taxon sampling for Azygiidae to date, molecular data from the ribosomal internal transcribed spacer 2 (ITS2) aided in confirming conspecificity among cercariae and adults of both Proterometra and Leuceruthrus, and did not reject the generic assignments of species described herein, or monophyly of either Proterometra or Leuceruthrus.